Studies of multi-ion-fluid yield anomaly in shock-driven implosions

A. NIKROO, GA -- Anomalously reduced yields relative to hydrodynamically calculated values have been observed for mixtures of D:$^{3}$He compared to pure D$_{2}$ gas-filled implosions in a series of shock-driven implosions at OMEGA. An extensive suite of measurements including temporal and spatial measurements of both the DD- and D$^{3}$He-fusion reactions were obtained to identify the origin and physics behind this anomalous yield reduction. Measured spectral linewidths of fusion products suggest that the D ions are not thermalized to $^{3}$He during the burn, contributing to the reduced yield. The hypothesis that ion-species separation due to diffusive processes contributes to the observed yield reduction is explored using hydrodynamic simulations incorporating ion diffusion. Recent observations by Rosenberg et al.\footnote{Rosenberg \textit{et al. Phys. Rev. Lett. }\textbf{112, }185001 (2014)} of a yield reduction with increased ion-ion mean free path do not explain the observed anomalous yield trend. Future work that will directly probe species separation with high-precision relative fusion reaction rate measurements between DD-neutrons and D$^{3}$He-protons using the DualPTD instrument is discussed. This work was supported in part by the U.S. DOE, NLUF, LLE, and LLNL.